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    // 通过数组拼接字符串 "a-b-c-d-e-f-g"
    // var list = ["a", "b", "c", "d", "e", "f", "g"];
    // var str = list.join("-");
    // console.log(str);

    
    // split()   用特定的字符 将字符串 分割形成数组
    // 返回值:数组

    // var str = "a-b-c-d-e-f-g";
    // var arr = str.split("-");
    // console.log(arr);

    // var str = "abcdefg";
    // var arr = str.split(""); // 将字符串拆分为单个字符 放到数组中
    // console.log(arr);


    // toUpperCase()    字母转大写
    // toLowerCase()    字母转小写   
    // 返回转化后的新字符串

    var str = "abcdefgHIJKLMN1234567你好";
    var result = str.toUpperCase();
    console.log(result);

    var str = "abcdefgHIJKLMN1234567你好";
    var result = str.toLowerCase();
    console.log(result);
 









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